diff --git a/dom/canvas/CanvasRenderingContext2D.cpp b/dom/canvas/CanvasRenderingContext2D.cpp
index 300ff8228a1..6fcff487091 100644
--- a/dom/canvas/CanvasRenderingContext2D.cpp
+++ b/dom/canvas/CanvasRenderingContext2D.cpp
@@ -4622,6 +4622,7 @@ CanvasPath::AddPath(CanvasPath& aCanvasPath, const Optional<NonNull<SVGMatrix>>&
     }
   }
 
+  EnsurePathBuilder(); // in case a path is added to itself
   tempPath->StreamToSink(mPathBuilder);
 }
 
diff --git a/dom/canvas/test/test_canvas_path.html b/dom/canvas/test/test_canvas_path.html
index 2a4ad2b8f5f..2e3fd3bf52d 100644
--- a/dom/canvas/test/test_canvas_path.html
+++ b/dom/canvas/test/test_canvas_path.html
@@ -378,6 +378,8 @@ function test_addpath_canvas() {
   shouldThrow(ctx, "p5.addPath(null, m)");
   shouldThrow(ctx, "p5.addPath([], m)");
   shouldThrow(ctx, "p5.addPath({}, m)");
+
+  p5 = p5.addPath(p5);
 }
 </script>